When most people see a map of the world, more often than not, it's based on the Mercator projection, which keeps all the lines of latitude horizontal, but warps the distances between the lines of longitude so that the farther from the equator you get, the more distorted the presentation of the features being mapped.

While that's useful for navigation, it does lead to some really big and all too common misconceptions about the true relative size of certain geographical features, like countries or continents. RealLifeLore explains in the following video:

If you want to move countries around to compare next to each other, you can at The True Size Of. Type in your country or countries of interest, then relocate it on the map to see how it really measures up in an overlay or a side-by-side comparison.